1. Technical Field
The present invention relates to apparatus and a method for retaining vertebrae of a spinal column of a patient in a desired spatial relationship. The invention will be described with particular reference to use as an anterior cervical spinal implant although it will be appreciated that the invention has wider application as will appear from the description that follows.
Cervical spinal implants are used to maintain a desired spatial relationship of cervical vertebrae in patients suffering from a number of conditions such as degenerative disc disease, trauma including fractures, tumours, deformity or failed previous fusions.
2. Description of the Prior Art
The usual procedure for decompressing and stabilising cervical spine over several segments involves the introduction of a long bone graft, harvested either from iliac crest or fibula, and stabilised with a rigid elongate perforated plate, screwed to the vertebra above and below the graft.
Whilst this usual procedure has provided satisfactory results in the past, there are numerous problems associated with it. First, it is difficult to introduce the bone graft into the vertebral defect under sufficient tension for the bone graft to be retained in a stable fashion. Secondly, the implanted plates sometimes work loose because the screws at either end are subjected to pull-out forces akin to those of a nail gripped by a claw hammer. Thirdly, because the screws are driven in from directly anteriorly, the vertical extent of the operative exposure is greater than the vertical extent of the vertebral defect, increasing the time, complexity and hazard of the procedure. Finally, the harvesting of the bone graft from iliac crest or leg is in itself a traumatic procedure and greatly adds to the patient's postoperative pain and disability, and prolongs rehabilitation.
It is an object of the invention to provide a spinal implant which provides stability to the spine, without the need for harvesting of a large bone graft from another part of the patient's body.